Didn't bother to watch the video, as I figured it was biased based on all the responses here. Anyhow, I've used both the D7k and K-5, but at the end of the day preferred the ergonomics and size of the K-5. To me AF was very similar between the two, despite the Nikon's "3D tracking" or "39 Point" AF. I tracked things moving horizontally and running towards me (mainly my dogs
) and found them to be similar. Nothing concrete, but that's my anecdotal experience. Most other old Nikon users profess the AF to still not be as good as the 300s.
I also want to mention that I've used the D7k with Nikon's "Pro Zooms". Namely the 14-24, 24-70, and 70-200 (newer Nikon holy trinity). Although the quality was great, the size and weight of those lenses are tremendous. Not to mention the cost.
Anyhow, I find it confusing when people want the D7k because it's cheaper than the K-5. Sure the body is cheaper, but if you really want a good lens (i.e. like the ones i mentioned), they are way more expensive then any Pentax equivalent. So I see overall pricing being a moot point unless you enjoy Nikon's lower lens offerings. But hey, whatever works for the user.